Apparatus for cracking hydrocarbons



Dec. 16, 1930.

w. MILLER 1,785,042 APPARATUS FOR CRACKING HYDROCARBONS Filed June 8, 1927 2 Sheets-Sheet l W. MILLER Dec. 16, 1930.

APPARATUS FOR QRAGKING HYDROCARBONS Filed June 8, 1927 2 Sheets-Sheet 2 WALTER MILLER, OF PONCA CITY, OKLAHOMA, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO CONTINENTAL OII COMPANY, OF PONCA CITY, OKLAHOMA, A CORPORATION OF Patented Dec. 16, 1930 UNITED STATES PATENT OFFICE DELAWARE Application filed June 8, 1927. Serial No. 197,289.

This invention relates to apparatus for cracklng hydrocarbons. One ofthe objects of the invention is to produce and recover the danger of destructive overheating in the crackingzone, and also increasing the capacity of the cracking apparatus.

Prior to this invention, cracking systems have been equipped with dephlegmators intended to condense and return to the cracking zone all fractions excepting the low boiling point fraction which passes to, the final condenser. The mixture of vapors generated in the cracking zone are ordinarily regarded as a low boiling point fraction to be recovered from the final condenser and a high boiling point fractionto be returned to the cracking zone. The high boiling point hydrocarbons, which usually return to the cracking zone, include hydrocarbons having various boiling'points, and thosehaving the lowest boiling points are most difiicult to crack. The ordinary reflux condensate, therefore, consists of the very high boiling point fraction which can be easily cracked and an intermediate fraction requiring higher temperaturesand longertime of reaction for conversion into the desired 10 boiling point fraction.

In other words, the vapors passmg from.

the cracking zone consist of a low boiling point fraction to berecovered from the final condenser, a high boiling point fraction which can be readily cracked and more refractory intermediate fraction requiring relativel high temperatures for further cracking. 11 following the ordinary practice of refluxing this intermediate fraction with the high boiling point fraction, the cracking zones must be maintained at a relatively high temperature for thecracking :of the refractory intermediate fraction, and this results in several disadvantages. A satisfactory cracking temperature cannot be maintained, because a temperature high enough to crack the refractory intermediate frac: tion is higher than the temperature necessary vtocrackthe high boiling point fraction,

APPARATUS FOR CRACKING HYDROCARBONS and if the temperature is too high there will be destructive overheating tending to produce permanent gas and also tending to destroy the cracking apparatus.- There is also a waste of fuel when the temperature is too high. In actual practice, the temperature is usually toofhigh forthe desired cracking ofthe high boilingpoint fraction and too low for the effective cracking of the refractory intermediate fraction, so the intermediate fraction is usually retained in the system for a long period in which it is repeatedly cooled in the dephlegmator and returned to the cracking zone, thereby causing undue loss of heat and also decreasing the capacity of the system.

In carrying outthe method hereafter de scribed all insufliciently cracked fractions can be returned to the'cracking zone, and the desired low boiling point fraction can be recovered from the final condenserin the usual manner. However, instead of trying to crack the refractory intermediate fraction and the high boiling point fraction at the same time and under the same conditions I have shown how the refractory intermediat-e fraction can be condensed and dis charged from the system, whilethe high boiling point fraction passes back to the cracking zone inthe form of reflux condensate.

It is thus possible to economize in the use,

diate fraction which, in the ordinary system,

circulates from the hot cracking zone to the cool reflux condenser and back to the hot zone, thereby occupying space in the system and wasting fuel by the continual reheating of the refractory hydrocarbons.

' The intermediate fraction may have a Baum gravity of 36 to 40 and it is cracked 1 sufiiciently to be used as fuel in oil burning furnaces. This fraction may therefore be regarded as a separate cracked product, or if desired it can be subjected to further cracking in a system designed for the high 1 temperatures necessary to crack the refractory hydrocarbons.

Another object of the invention is to wash the low boiling point gasoline vapors by bubbling them through pools of liquid formed by the intermediate fraction. In the preferred form of the invention, the dephlegmator includes a refluxing zone wherein the high boiling point fraction is condensed, a bubbling zone where the intermediate fraction is condensed and discharged from the system, and a heat exchanger beyond the hubbling zone. The incoming charging stock passed through the heat exchanger and then into the refluxing zone without entering into the liquid in the bubbling zone. The charge is thus preheated and passed around the intermediate fraction in the bul bling zone so as to mix with the high boiling point fraction in the refluxing zone.

With the foregoing and other objects in view, the invention comprises the novel con struction, combination and arrangement of parts hereinafter more specifically described and illustrated in the accompanying drawings, wherein is shown the preferred embodiment of the invention. However, it is to be understood that the invention comprehends changes, variations and modifications which come within the scope of the claims hereunto appended.

Fig. 1 is a vertical section illustrating a dephlegmator embodying the features of this invention.

Fig. '2 is a diagrammatical view on a smaller scale showing the dephlegmator associated with other elements of a cracking system.

To illustrate one form of the invention, I have shown a cracking system of the tube and tank type comprising a cracking coil 1 provided with a transfer line 2 leading to a separating chamber, or vaporizing chamher 3, the latter having an outlet 4 for the discharge of residuum. A vapor pipe 5 extends from the chamber 3 to a dephlegmator A. A vapor pipe 6 extends from the top of the dephlegmator to a final condenser 7. A valve 8, located in the discharge pipe 9 beyond the final condenser, may be adjusted to maintain the system under a high pres sure. The raw chargin stock is supplied through a pipe 10 leading to a heat exchanger in the form of'a coil 11 in the upper portion of the dephlegmator, and a pipe 12 extends from this coil to the lower portion of the dephleglnator for the purpose of conducting the preheated charging stock into the vapor space. The mixture of charging stock and reflux condensate accumulates at 13 to form a reserve supply which passes through a pipe 14- to a pump 15 and thence through a pipe 16 to the cracking coil 1. This coil may be heated in any suitable manner to obtain the desired cracking temperature.

The dephlegmator is exposed to the air for cooling and it comprises a refluxing zone provided with baflies 17, a bubbling zone above the refluxing zone and heat exchanger 11 above the bubbling zone.

The bubbling zone comprises a bottom plate 18 with a vapor passageway 19 at the center and higher plates 20 provided with vapor passages 21 and caps 22 arranged over said passages to form liquid seals around them. Each of the plates 18 and 20 supports a pool of hydrocarbon liquid. The condensate formed in this zone flows downwardly through overflow pipes 23, and it is discharged from the lowermost pool through a pipe 24 extending from said pool to a storage tank 25. Valve 26 is located in the pipe 2 1.

The insufiiciently cracked high boiling point fraction is condensed in the refluxing zone provided with the battle plates 17, and this fraction returns to the cracking coil with the preheated charging stock passing from pipe 12. It will be noted that the charging stock passes through the pipe 12 from the heat exchanger 11 to the refluxing zone without entering the liquid in the hubbling zone.

The intermediate fraction is condensed in the bubbling zone and at the heat exchanger 11 above said zone. The pools of liquid in this zone are maintained at temperatures low enough to condense a portion of the intermediate fraction, and the heat exchanger is maintained at a still lower temperature to condense the other portion of said fraction.

The vapors of the low boilingpoint fraction are washed and purified in bubbling through the pools of liquid, and these vapors pass on to the final condenser 7 where tl ey are condensed to form the low boiling point product.

The intermediate fraction withdri'nvn from the bubbling zone is a cracked product having a boiling point range between 360 and 650 F. and is suitable for a burning oil, fuel oil for furnaces, fuel for internal combustion engines and for other purposes, or it may be subjected to further cracking in suitable high temperature equipment.

I have already referred to the several advantages obtained by removing the interme diate fraction from the cracking system, in stead of permitting it to return to the cracking zone. Further advantages are gained by the dephlegmator herein shown. It is desirable to use bafile plates 17 in the refluxing zone and to shower the liquid from one plate to another, but when such plates are used alone, some of the high boiling point fractions are carried on with the vapors in the form of mist. In the dephlegmator I have shown, the fractions just referred to are trapped in the bubbling: zone and discharged with the intermediate fraction, instead of passing to the final condenser. The intimate contact of vapors and liquid in the bubbling zone results in a very eflective separation r of the intermediate fraction from the low boiling point fraction, and the impurities washed from the low boiling point vapors are discharged with the intermediate fraction and prevented from either returning to the crack- 10 in g zone or passing to the final condenser.

I claim:

1. In an apparatus for cracking hydrocarbons, a cracking element maintained at a cracking temperature, a dephlegmatcr receiving the vapors from said cracking element, said dephlegmator comprising a refluxin g zone wherein the highest boiling point fraction in said vapors is condensed, and a relatively cool bubbling zone provided with pools of hydrocarbon liquid through which vapors are discharged from said refluxing zone, the vapors from said refluxing zone being passed through said pools of liquid, an inlet device whereby charging stock is v delivered to the reflux condensate formed in said refluxing zone, said inlet device being adapted to prevent the delivery of said charging stock to said bubbling zone, means whereby the mixture of reflux condensate g0 and charging'stock is'delivered to said cracking element, a storage receptacle, and a discharge device leading from said bubbling zone to said storage receptacle so as to remove the intermediate condensate from the cracking system.

2. In an apparatus for cracking hydrocarbons, a cracking element maintained at a cracking temperature, a dephlegmator receiving the vapors from said cracking element, said dephlegmator comprising a refluxing zone wherein the high boiling point fraction is condensed, a relatively cool bubbling zone provided with pools of hydrocarbon liquid through which vapors are discharged from said refluxing zone, the vapors from said refluxing zone being passed through said pools of liquid in said bubbling zone, a heat exchanger located beyond said bubbling zone to receive the vapors passing therefrom, a final condenser beyond said heat exchanger, meansv whereby charging stock is passed through said heat exchanger and then into said refluxing zone without entering into the liquid in said bubbling zone, LL means whereby the mixture of charging stock and reflux condensate is transmitted from said refluxing zone to said cracking element,

a storage receptacle, and a discharge conductor leading from said bubbling zone to 1 said storage receptacle so as to discharge the condensate from said bubbling zone to said storage receptacle.

In testimony that I claim the foregoing I hereunto aflix my signature.

WVALTER MILLER.

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